In the context of mobile data and communications networks, such as third generation (3G) and fourth generation (4G) (e.g., long-term evolution (LTE)) wireless access technologies, a service provider may use authentication and key agreement (AKA) techniques to determine whether a mobile device, such as a smart phone, is authorized to access services. The mobile device may include hardware and/or software, such as a subscriber identity module (SIM) or a removable user identity module (R-UIM) to provide an AKA response, and the AKA response may include information identifying the mobile device, such as an International Mobile Subscriber Identity (IMSI). The IMSI typically includes fifteen (15) digits. For example, the IMSI may include a three digit mobile country code (MCC), a nine or ten digit mobile subscriber identification number (MSIN), and a two or three digit mobile network code (MNC).
The service provider may store at least a portion of IMSIs (e.g., the MSINs) associated with authorized mobile devices, (e.g., in a home subscriber server (HSS)), and the service provider may authenticate a requesting mobile device by determining whether the mobile device has forwarded an IMSI value that matches one of the stored IMSIs. In another example, the service provider may, after initially authenticating the mobile device using the IMSI, assign a temporary mobile subscriber identity (TMSI) to the mobile device and may subsequently authenticate the mobile device using the TMSI.